1. Field of the Invention
The present invention pertains to a system in which there is a working fluid that passes through a rotary machine whose rotor is within a working chamber and which has a power shaft extending from said chamber through an opening in the wall thereof to the exterior thereof to transmit power between the interior of the chamber and the exterior thereof. It is specially adapted to a system in which a working fluid has power added thereto in the form of heat, after which it is passed through the working chamber and the rotor of the machine to give up its power and be recirculated to receive more heat power. The working fluid is thus captive and the purpose of the seal system of this invention is to conserve said fluid and prevent its loss by leakage from the working chamber along the shaft. Such shafts are frequently required to rotate at extremely high speeds such as to prohibit the use of seals of mechanical engagement type, making it necessary to resort to so-called fluid seals in which a fluid is injected into a small annular clearance between the shaft and its surrounding structure, intermediate the ends of such clearance, so that the fluid will flow in both directions at its point of injection. Such a system is illustrated generally in my prior U.S. Pat. No. 3,831,381, issued Aug. 27, 1974, on an application filed May 2, 1973.
The term "fluid" is used herein to designate a flowable medium, either gas or liquid.
In systems of this kind, the housing in which the rotor is located and through an opening in which the shaft emerges typically has bearings for the shaft with bearing surfaces on the shaft and within the opening in the housing through which the shaft passes. Such surfaces are dimensioned so as to be spaced apart sufficiently to permit a lubricant to be introduced at an intermediate point between the two bearing surfaces at such pressure as to cause it to flow in both directions from such intermediate point. In this arrangement, the lubricant flowing between the bearing surfaces toward the rotor prevents flow of the working fluid in the opposite direction and thus prevents its leakage from the system along the shaft. In order to prevent the liquid lubricant from becoming contaminated with working fluid, or vice versa, provision is made for withdrawing from between the shaft and housing at a point intermediate the rotor and the bearing, the lubricant flowing from the bearing toward the rotor and the working fluid flowing from the rotor around the shaft toward the bearing. However, this produces inevitably a rather intimate contact between these two fluid media causing them to mingle and to a greater or lesser degree dissolve in or react with one another. The result is an intermingled mixture or compound from which the components of lubricant and working fluid must be extracted if they are to be reused. The result is potential loss of working fluid or of lubricant or the desirable properties of one or the other, or in the alternative, a substantial expenditure in energy and equipment requirement in resegregating such components.
2. Description of the Prior Art
In my prior patent above mentioned, a labyrinth type seal is located around the shaft intermediate the rotor and the lubricated bearing and into this seal is injected a seal fluid, which may be a seal gas, but which is, in the specific illustration in said patent, a constituent of the working fluid. This seal gas or vapor, flowing through the labyrinth type seal in both directions from its point of injection, intermingles with the working fluid in the chamber in which the rotor is located, and intermingles with the lubricant in a chamber between the labyrinth seal and the bearing seal, from which chamber a mixture of lubricant and the seal gas are withdrawn. The seal gas is selected to be of such a character that it will not substantially dissolve in nor react with the lubricant. Hence in said patent, when they are withdrawn in more or less intermingled relation with one another, they may be readily separated from one another so that the lubricant from such separation step may be recirculated and reused and the seal gas may likewise be reused. Such seal gas, to be reused may be conveniently injected into the stream of working fluid leaving the chamber in which the rotor is located, and then recirculated with such working fluid to the point where the working fluid is heated for reuse. In this step, the seal gas component is, in said patent, separated from the remainder of the working fluid by fractional distillation or the like and then circulated back to the point of injection into the labyrinth seal, where it begins a new cycle.
Clearly the system set forth in my said prior patent requires the expenditure of a substantial amount of heat energy in separating the seal gas from the working fluid each time it passes through its cycle. Such heating, followed by the natural cooling and then reheating of the working fluid constituent employed as a seal gas naturally results in some additional loss of heat energy.